This invention relates to the fields of dielectrophoresis phenomena, inanimate material non-uniform surface electric field patterns and spatial gradient patterns caused by naturally-occurring static electrification. More particularly, the invention relates to the hitherto unattainable detection and location of inanimate materials by coupling the non-uniform electric field spatial gradient pattern via dielectrophoresis to a characteristic force and subsequent torque on a high aspect ratio (length/radius) antenna and selective dielectric polarization matching and filtering components in a locating device giving a real-time updated line-of-bearing to the inanimate material maximum surface electric field spatial gradient and hence to the inanimate entity itself, even if an entity is located behind vision-obscuring barriers made of metals, dielectrics, plastics, earth, wood, etc. and/or EMI is present.
The detection of visually obscured entities has many uses in fire-fighting, search and rescue operations, law enforcement operations, military operations, etc. With respect to inanimate entities, such as specific polymers, plastics, and other organic/inorganic materials, additional applications may include transportation security in pre-boarding planes, trains and automobiles, new and old construction industry, law enforcement, military operations, anti-shoplifting protection and other security needs/operations. While prior art devices are known that detect humans, animals and other materials, some by measuring changes in an electrostatic field, none of the operable prior art devices uses the force resulting from the non-uniform electric field squared spatial gradient three-dimensional pattern exhibited uniquely by an entity to indicate the precise location and direction of the subject entity relative to the device""s operator.
By using an electrokinetic effect, dielectrophoresis, which induces a force and subsequent resulting torque on an antenna and other component parts of the device, the present invention gives a rapid directional location indication of the subject entity. A meter can also be provided to indicate the direction of strongest non-uniform electric field squared spatial gradient signal strength for those situations where the dielectrophoretic force and subsequent resulting torque, acceleration, vibration or any other measurable quantifiable manifestation of the force is extremely small and difficult to detect.
It should be noted that while the present invention works for many different types of entities, a primary use of the present invention is to locate inanimate entities, irrespective of the presence or absence of obscuring material structures (walls, trees, earthen mounds, etc.), rfi and emi interference signals, adverse weather conditions, and day or night visibility conditions.
Dielectrophoresis describes the force and subsequent torque mechanical behavior of initially neutral mater that is dielectric polarization charged via induction by external spatially non-uniform electric fields. The severity of the spatial non-uniformity of the electric field is measured by the spatial gradient (spatial rate of change) of the electric field. The fundamental operating principle of the dielectrophoresis effect is that the force (or torque) generated always seeks to point in the same direction, toward the maximum local electric field spatial gradient, independent of sign (+/xe2x88x92) or time (AC/DC). See, H. A. Pohl, Dielectrophoresis, Cambridge University Press (1978) and H. A. Pohl, Electrostatics and Applications, Chapters 14 and 15, A. D. Moore (editor), Interscience Press (1973).
The nature and source of the inanimate entity""s (in particular plastics) electric field and its spatial gradient being detected in the dielecrophoresis effect generating the directionally self-correcting force and subsequent torque characteristic of an animate entity line-of-bearing locating device has been discussed in Static Electrification, P. Secker, University College North Wales (1976); D. J. Montgomery, Static Electrification of Solids, Solid State Physics, 9, 139 (1959); W. R. Harper, Contact and Frictional Electrification, Oxford Press (1967); R. Cunningham, Static Electrification, Physics Encyclopedia, 891 (1974); I. Inculet in Electrostatics and Applications, Chapter 5, supra; G. H. Johnson, Polymer Films Static Electrification, DuPont (1974 to 1979). The empirical evidence in the case of inanimate materials is quite persuasive that the inanimate objects"" naturally-occurring static electrification generates a small ULF (10xe2x88x923 Hz to 2 Hz) electric field and spatial gradient pattern.
Static electrification proceeds via naturally-occurring contact charging (static/dynamic) including transfer of electrons, ions, charged chemical species and via the intimate interfacial phenomena triboelectric charging. Static electrification also proceeds via artificially-occurring industrial processes using static charging by corona, flame, electron beam, radiation and induction. Static electrification phenomena occur in industrial and domestic life via highly insulating nonconducting materials such as polymers and plastics.
Naturally-occurring static electrification via wind and water currents causes detection information transfer allowing orientational/navigational abilities and activities of birds, bees and fish. See, Electromagnetic Bio-Information, F. Popp, et al. (eds.), Urgan Publ. (1979); Handbook: Biological Effects of Electromagnetic Fields, C. Pol, CRC Press (1966) Sensory Biology of Aquatic Animals, J. Aetma, et al. (eds.), Springer (1988); Orientation: Sensory Basis, H. E. Adler, 188, 271 91971). For semi-conducting human bodies, but not for highly insulating plastics, static electrification effects, while nuisances, are short-lasting effects, neutralized by RH, or leaked to the ground. Bulk human decay times are about 10xe2x88x923 sec.
The very high electrical resistivity of widely-used plastics as materials-of-construction does not allow the static electrification charges to leak harmlessly to ground. On the contrary, the charges are continuously accumulated at a particular location or on the surface building up very high electrical surface voltages up to tens of kilovolts. The static electrification charges on plastics are very long-lasting, with characteristic times for exponential decay of 102 sec. (polyester) to 106 sec (Teflon(copyright)) (minutes to days). This is generally referred to as sub-ULF (0 to 3 Hz) and ULF (3 to 30 Hz) frequencies. In the ULF and sub-ULF ranges as discussed in D. O. Carpenter, Biolozical Effects of Electromagnetic Fields, Academic Press (1994), the electric and magnetic fields are quasi-static, are not strongly coupled as xe2x80x9cEM waves,xe2x80x9d and EM activity detected in this range have predominantly either electric or magnetic nature. See J. Heirtzler, Sci. Am. 205, 3, 128 (1962); S. Mende, Sci. Am. 204, 8 (1997); S. Carlson, Sci. Am. 239, 5, 98 (1996). The voltage decay time constant depends on the material""s inherent electrical resistivity and dielectric constant describing plastics conduction and polarization properties as discussed in Properties of Polymers, D. van Krevelen, Elsevier Publ. (1976); A. R. von Hippel, Dielectrics and Waves, John Wiley and Sons (1954); and Dielectric Materials and Applications, A. R. von Hippel, John Wiley (1954). The irregular, pervasive nature of static electrification ensures long-lasting electric field patterns having significant spatial gradients. The voltages, electric fields and electric field spatial gradient decrease as one moves away from the surface of the plastics material. In addition, various surface free/bound-charge electron traps exist on all materials, particularly plastics. See, Physical Chemistry of Surfaces, A. W. Adamson, Interscience Publ. (1967); Excess Electrons in Dielectric Media, C. Ferradini (ed), CRC Press (1991).
Static electrification effects are further divided into threshold and non-threshold type phenomena. Dust and debris accumulation, as well as xe2x80x9cstatic clingxe2x80x9d are examples of non-threshold static electrification effects as are the build-up of surface voltage, electric field and electric field spatial gradient. Other static electrifcation effects, like electrical discharges, spurious images, capacitor breakdown, explosions and anomalously strong adhesion, are examples of threshold effects. Static electrification voltage effects (electric fields and electric field gradients on dielectric materials, particularly plastics, charge-up following an exponential build-up equation:
V(t)=V0(1xe2x88x92exe2x88x92t/xcfx84) and discharge as V(t)=Vxe2x88x92exe2x88x92t/xcfx84
wherein xcfx84=time constant with three components: 1/xcfx84=1/xcfx84B+1/xcfx84S+1/xcfx84R where xcfx84B=bulk time constant, xcfx84S=surface time constant, and xcfx84R=irradiation time constant. The bulk time constant is related to the bulk electrical resitivity (xcfx81) and K, the bulk dielectric constant, via: xcfx84B=xcfx81K∈0; ∈0=free space permittivity =8.85xc3x9710xe2x88x9212 farad/m. The surface time constant is related particularly to the inverse of the relative humidity in the atmosphere. The radiation time constant is related particularly to the inverse of the amounts of positive and negative charged species in the atmosphere. For example, Polonium 210 is a prolific source of both positively and negatively charged nuclear species, providing for a very short irradiation time constant.
The dependent variable of interest for the present invention is the levels and time dependence of the surface voltage, electric field and electric field spatial gradient. These dependent variables are considered as functions of numerous independent variables: material variables (bulk and surface chemical composition and structure; bulk and surface electrical resistivities, contact potential differences and dielectric constants; molecular and structure, orientation and crystallinity; state of strain; size and shape; initial state of electrical charge); ambient conditions (relative humidity, temperature, atmospheric composition and pressure and presence of stray, interfering electromagnetic fields (EMI)); and mechanical variables (type of contact (touching, impacting, rubbing, rolling, twisting, etc.); orientation of bodies during contact; area of contact (including path length); duration of contact; relative velocity of materials; normal and tangential forces between the materials). The static electrification build-up and time dependence and decay of the surface voltage, electric field and spatial gradient are due to excess charge transfer and its future behavior.
Traditionally, inanimate dielectrics have been found to exhibit three main and one rare polarization modes (electronic, atomic, orientation and the rare nomadic) as discussed in Properties of Polymers, D. W. van Krevelen, Elsevier Publ. (1976); A. R. von Hippel, Dielectrics and Waves, John Wiley and Sons (195); Dielectric Materials and Applications, A. R. von Hippel (ed) John Wiley (1954); H. A. Pohl, Dielectrophoresis, Cambridge University Press (1978). These modes lead additively in the sequence given as one goes from UHF (1018 Hz) to ULF (3 to 30 Hz) to sub-ULF (0 to 3 Hz) dielectric constraints of 1.0 for air to 78 for water with essentially all plastics in a 3 (PVC) to 14 (Bakelite) range. There are rare outriders like the solvent NMMA at 191, Se at 1xc3x97103 and ferroelectric BaTiO3 and rare nomadic polymers (CS2)x at 2xc3x97104 and PAQR carbazole at 3xc3x97105.
Mammalian physiology results for the ULF dielectric constants of mammalian (human) living tissues, wherein mammalian (human) tissues are 70% volume water (dielectric constant 78), show that all the ordinary animate human tissues, like heart, brain, liver, heart, blood, skin, lung and even bone, have quite extraordinarily very high ULF dielectric constants (105 to 107), found only very rarely in usual inanimate dielectric materials. See Biomedical Engineering Handbook, J. D. Bronzino (ed.), CRC Press (1995); Physical Properties of Tissue, F. A. Duck, Academic Press (1990); H. P. Schwan, Advances in Biological and Medical Physics, 5, 148 to 206 (1957); E. Grant, Dielectric Behaviour of Biological Molecules, Oxford Univ. (1978). It is also found that, as the animate tissues die, these extraordinarily high ULF dielectric constant collapse downward greatly to more normal inanimate values over time as the dying tissue becomes over time inanimate. The reason for the great differences is the routine occurrence of other polarization modes in animate materials, but which occur very rarely in inanimate materials. These other polarization modes are interfacial (inhomogeneous materials) and pre-polarized elements which occur readily in all animate tissues. It is known that the rest state of the human neural, cardiac, skeletal muscular and sensory systems are states of high polarization. Therefore, the extraordinarily high dielectric constant for the human operator causes the static electrification electric field lines and spatial gradients to be directionally distorted toward a human operator of the locator device, hence increasing the electric field line flux density, which is directly related to an increase in the device""s sensitivity.
Dielectrophoresis has been practiced using nearly exclusively artificially-set-up external non-uniform electric field patterns in laboratories to dielectrically separate individual em-size mammalian cells or small (xcexcm) inanimate, inorganic particles. See, H. A. Pohl, Dielectrophoresis, Cambridge University Press (1978) and T. B. Jones, Electromechanics of Particles, Cambridge University Press (1995). The problems of this prior art in trying to observe dielectrophoresis force and torque effects in meter-size ensembles of tens of billions of xcexcm-size inorganic particles chemically coupled together and working in concert as an inanimate entity are overcome by utilizing naturally-occurring pervasive static electrification effectsxe2x80x94surface ULF electric fields and electric field spatial gradients. Table I lists the charging and discharging time constants for some well known plastic materials.
FIG. 1 illustrates static electrification of an inanimate entity 10; where material one 11 and material two 12 are in mutual and intimate contact with inanimate entity 10 at interfaces 13 and 14, respectively, moving at speed V1 and V2 with respect to the inanimate entity 10. The amount and sign of the electrical charges (voltages, electric fields and electric field spatial gradient) exchanged at the two interfaces 13, 14 via static electrification depends upon the relative positions of the materials 11, 12 and the inanimate entity 10 on the triboelectric series 20 (and other factors), wherein positions on the triboelectric series are determined by the dielectric constant 21 and environmental conditions (dry or wet). See FIG. 2. The static electrification charging and discharging time constants xcfx84 of materials 11, 12 and inanimate entity 10 depend also upon their bulk electrical resisitivites xcfx81 via equation xcfx84=xcfx81K∈0 as previously discussed.
FIG. 3 shows the correlation between bulk electrical resistivity xcfx81 31 and the dielectric constant K 32. The bulk charging and discharging time constant (xcfx84) is related to these factors via the equation xcfx84=xcfx81K∈0; where ∈0=free space permittivity=8.85xc3x971012 F/m and unit for xcfx81 is (xcexa9-m)xe2x88x921. Note F/xcexa9=sec. FIG. 4 shows a typical static electrification electric field spatial gradient where a positively charged 40 polymer web 41 has a very uniform electric field lines 42, (low electric field spatial gradient), far from the a grounded metal roller 43, but near the grounded metal roller 43, the electric field lines 44 become very low over a very short spatial distance, creating an extremely large spatial gradient for the electric field lines just as the positively charged 40 polymer web 41 enters the xe2x80x9cnipxe2x80x9d 46 of the grounded metal roller 43.
FIGS. 5(a) and 5(b) show the exponential growth 51 and decay 52 curves, respectively for surface voltage, electric field (spatial gradients) resulting from the static electrification and de-electrification of an (see FIG. 1) inanimate entity""s 10 surface by the materials 11 and 12, with which it is in mutual and intimate contact. FIG. 6 shows ideal ULF waveform 60 for repeated charge 61 and discharge 62 cycles due to static electrification and de-electrification of the surface of an inanimate entity 10 by the materials 11 and 12.
The present invention relates to a locator device that detects the presence of various entities using an electrokinetic effect known as dielectrophoresis. Dielectrophoresis is one of five known electrokinetic effects (the other four being electrophoresis, electro-osmosis, Dorn effect, and streaming potential) and describes the forces affecting the mechanical behavior of initially neutral matter that is dielectrically polarized by induction via spatially non-uniform electric fields. The spatial non-uniformity of an electric field can be measured by the spatial gradient of the electric field. The dielectrophoresis force depends non-linearly upon several factors, including the dielectric polarizibility of the surrounding medium (air plus any intervening walls, trees, etc.), the dielectric polarizibility and geometry of the initially neutral matter (device""s antenna and other component parts of the device), and the spatial gradient of the square of the target""s local electric field distribution induced by static electrification as detected at the device""s antenna and other component parts. The spatial gradient is measured by the dielectrophoresis force produced by the induced polarization charge on the device""s antenna and other component parts, and this force is a constant direction seeking force always pointing (or trying to point) the device""s antenna and other component parts toward the maximum gradient in the three-dimensional non-uniform electric field squared spatial gradient pattern uniquely exhibited by a predetermined entity type.
The constant direction seeking force is highly variable in magnitude as a function of the angular position and radial position of the entity-to-be-located with respect to the device""s antenna and other component parts of the device, and upon the effective dielectric polarizibilities of the intervening medium (like air) and of the materials used in the device""s antenna and other component parts. The following equations define the dielectrophoresis forces wherein Equation 1 shows the force for spherical initially neutral objects (spherical antenna and the device""s other component parts), and Equation 2 shows the force for cylindrical initially neutral objects (cylindrical antenna and the device""s other component parts).
F=2(xcfx80a3)∈0K1(K2xe2x88x92K1)/(K2+2K1)∇|E0|2xe2x80x83xe2x80x83Equation 1
F=L/a(xcfx80a3)∈0K1(K2xe2x88x92K1)/(K2+K1)∇|E0|2xe2x80x83xe2x80x83Equation 2
Where:
F is the dielectrophoresis force vector detected by the antenna and the device""s other component parts;
a is the radius of the sphere or cylinder;
L is the length of the cylinder (L/a is the so-called axial ratio);
∈0 is the permittivity constant of free space;
K2 is the dielectric constant of the material in the sphere or cylinder;
K1 is the dielectric constant of fluid or gas, (air) surrounding both the entity and the antenna and the device""s other component parts;
E0 is the electric field produced by the entity as detected by the antenna and the device""s other component parts; and
∇ is the spatial gradient mathematical operator.
It should be noted that the term xe2x80x9cantennaxe2x80x9d as used in this context includes (in a very real sense) all of the components present in the device of the present invention, including the living human operator. To this extent, the dielectric constant of the materials that make up the locator and the living human operator of the present invention all determine the overall value of K2 in the above equations. These materials are not arranged in a uniform spherical or cylindrical shape, and therefore the exact value of K2 and the functional relationship of K2 to K1 are difficult, if not impossible, to determine in a closed form of a mathematical equation. In a practical sense, experimentation has shown (and is continuing to show) the types and placement of dielectric materials needed to produce a maximum dielectrophoretic force and subsequent resulting torque, acceleration, vibration or any other measurable quantifiable manifestations of the force for precisely locating different types of entities. The following table lists some of the dielectric materials possibly used in the locator (K2 values) and/or surrounding (such as air, water, walls, etc.) the locator (K1 values) and the dielectric constant for these materials.
The above discussion and equations concerning dielectrophoresis provide a rational explanation of the operating principles of the present invention that is consistent with all empirical observations associated with the present invention. These operating principles involve using the above-mentioned forces to point an antenna toward the maximum spatial gradient of the local electric field, to thereby indicate the direction toward an unseen entity.
In accordance with the invention, an operator holds the locator device in hand, and through a handle, the locator device is electrically connected to the operator. The operator is partially electrically grounded (through the operator""s feet), and thereby the individual human operator body""s capacitance (C) and resistance (R) to true ground are connected electrically to the handle of the locator device. Ranges for individual human body""s C have been measured as 100 pF to 400 pF and for individual human body""s R have been measured as 0.03 Kxcexa9 to 1 Mxcexa9. Thus, the generalized electrical parameter (the polarization charge pattern induced on the device by the electric field spatial gradient of the entity in this case, but also electric field, current and voltage) exponential decay time (=RC) constant range for the variety of human being bodies potentially acting as locator device operators is about 3 to 400 xcexc seconds. This decay time constant is greatly increased through an externally connected series resistor of up to 100 Kxcexa9 and parallel capacitor up to 0.01 mF, which results in an effective human operator""s exponential decay time constant up to 1 to 10 seconds.
This enables dielectrophoretic forces caused by the induced polarization charge pattern on the locator device antenna and other component parts to be detected, replenished instantly and locked onto since the force is replenished faster than the induced polarization charge pattern on the device can decay away to true ground through the operator""s body. This effect is called, and is using, the spatially self-correcting nature of the dielectrophoretic force (always pointing or trying to point to the maximum of an entity""s electric field three-dimensional squared spatial gradient pattern, which in the case of inanimate entities, is static electrification induced.
The locator device is held in a balanced, few degrees down tilt from the exactly horizontal state, and the operator scans the locator device in a constant speed uniform linear motion back and forth. An antenna extends from the front of the locator device and is acted on along with the device""s other components by the aforementioned forces. These forces create a subsequent resulting torque around a well defined pivot line which tends to make the locator device""s antenna and the device""s other component parts point toward the maximum spatial gradient of the square of the non-uniform electric field uniquely exhibited by any target entity within the range of the locator device.
Four internal N-channel J-FETs (field effect transistors) are connected to the locator device""s antenna and operate in their non-linear range to effectively change the antenna""s length. Three of these FETs are arranged in modules that are equidistant from the antenna""s longitudinal axis and are spaced 120xc2x0 apart. The fourth FET is arranged in a module below the axis and to the rear of the locator device. Three potentiometers are provided on the first three modules to adjust the current levels through the first three FETs and thereby tune the locator. The gain and frequency response of the fourth FET is adjusted by a six position switch connected to the base of an NPN transistor. By changing the frequency response of the locator device, the device is tuned to reject the higher frequency electromagnetic signals and noise from all external sources, including those sources associated with the human operator himself in order for the locator device to interact with and respond to only the three-dimensional non-uniform electric field squared spatial gradient pattern exhibited uniquely by a predetermined entity type.
While scanning the locator device in a constant speed uniform linear motion back and forth in front of a known or reference entity, the operator changes the six position switch until a maximum force and subsequent resulting torque is detected and used to aim the antenna and the device""s other component parts toward the target entity. After selecting the setting of the six position switch, the operator adjusts the gain of the first three FETs until the locator device points or tries to point directly at the target entity. For different entities, different dielectric materials are used for the antenna and other component parts. Examples of detectable entities include metals, plastics, polymers and other inanimate materials. Continued research on the instrument has yielded positive results in the instrument""s ability to be tailored both as a geometrical design and with respect to materials of construction to specifically detect a variety of different target entities. Accordingly, it is an objective of the invention to provide an accurate method of locating the direction and position of target entities relative to a human operator. It is another objective of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.